Refrigerator heat interchanger



Aug. 29, 1939. E. GYGAX REFRIGERATOR HEAT INTERCHANGER Filed Marph 20, 1936 m H mm m V T mm .M q. E M w W 5 m w an nun I! 7 a 7 r 4 ",EQH. "a a MM,

W a 5 7 G A. 0 a y Patented Aug. 29, 1939 PATENT OFFICE REFRIGERATOR HEAT INTERCHANGER Ernest Gygax, St. Louis, Mo., assignor to Curtis Refrigerating Machine Company, Wellston, Mo., a corporation of Missouri Application March 20, 1936, Serial No. 69,875

9 Claims.

This invention relates to heat interchangers for use in a refrigeration system.

In a conventional form of refrigeration system, a gas is compressed, condensed, and allowed to 5 expand in evaporator coils from where it is drawn into the compressor to be compressed again. Usually an approximate state of balance exists between the load on the evaporator coils and the capacity of the compressor. Such a sys- 10 tem operates satisfactorily so long as the load on the evaporator coils is approximately constant. It is often desirable, however, to use one compressor for two or more evaporator coils. During certain periodsall of the evaporator coils 15 may be in use while during other periods only one or two of the coils may be used. Since the compressor capacity selected must be sufiicient to supply the total number of evaporator coils, its capacity will be too great when only one or two 20 of the evaporator coils are used. As a consequence thereof, the evaporator coils will not sufficiently evaporate the refrigerant, and liquid or partially liquid refrigerant will be drawn into the compressor. This causes compressor failure due 25 to refrigeration taking place in the crankcase, seizing of bearings, dilution of oil, locking of pistons by the liquid, as well as other mechanical failures.

The conventional type of refrigeration system, 3 operating on the above described cycle, for example, is used in many types of air conditioning systems, the air for cooling the room being cooled by blowing it over the evaporator coils by means of fans or blowers. In order to control the 35 amount of air thus cooled, so as to regulate the temperature of the air conditioned room with regard to the prevailing outside temperature, a multispeed blower is often used. A change in the speed of the blower results in a change of the 40 load on the evaporator coils causing the load on the evaporator coils to be out of balance with the capacity of the compressor and producing the results set forth above which usually accompany an out of balance state between evaporator load 5 and compressor capacity. To avoid these results it has been necessary in such systems to employ a'variable speed compressor motor, the

speed of which is varied in accordance with the speed of the blower motor. This method of avoiding the difliculty, however, introduces the disadvantages of a multispeed compressor motor.

Many refrigeration-systems are in use on combination ice cream freezers and storage cabinets where a number of evaporator coils are used with 55 a single compressor. Some of the evaporator coils are used for freezing the ice cream while others are used for cooling a storage cabinet for hardening and storing the product of the freezer. The evaporator coils in the freezer, while of large capacity, are used for only a relatively small por- 5 tion of the time, being shut off after the required amount of the product is frozen. The sudden shutdown of the evaporator coils in the freezer results in more liquid refrigerant being produced than the remaining evaporator coils can evaporate to a gaseous state, resulting in liquid refrigerant being drawn into the compressor and subsequent compressor failure.

It is an object of this invention to provide a heat interchanger which, when connected in the compressor suction line and allowed to interchange heat with the uncondensed gas or liquid from the condensing unit, will avoid the disadvantages above set forth.

Thus one of the objects of the present invention is to provide a heat interchanger which will compensate for a lack of balance between evaporator loads and compressor capacity.

Another object of the invention is to provide a heat interchanger which will prevent any liquid refrigerant being drawn into the compressor after a shutdown period of the condensing unit.

Still another object is to provide a heat interchanger which will prevent back freezing to the compressor when it is desired to have a constant coil temperature with varying loads.

Yet another object is to provide a valve means which will act as a by-pass between liquid in the receiver and the suction line entering the heat interchanger, which valve can be controlled by various means to act in conjunction with the heat interchanger as a balancing device between the evaporator load and the condensing unit.

The above and other objects are accomplished in the present invention by providing a heat interchanging means between the gas entering the compressor and the refrigerant leaving the condenser. Normally a condenser extracts only a part of the heat of the compressed refrigerant so that the refrigerant leaving the condenser may consist of the refrigerant in liquid form as well as some hot uncondensed gas, either of which retain some of the heat received during the compression process, which heat can be interchanged with the gas entering the compressor. Since condensers are cooled by air or water, a fluctuation of either the temperature or amount of air or water used to cool the condenser will affect the temperature of the refrigerant leaving the condenser. Because of seasonal weather changes, 5'

combination liquid receiver and heat inter-' changer in combination with an automatic conpara.

if no adjustment is made in the operation of the condenser cooling. means, the temperature of the refrigerant leaving the condenser fluctuates through too wide a range to insure satisfactory operation of the heat interchan'ger.

It is therefore another object of this invention to provide an automatic means for regulating the temperature of the refrigerant leaving the condenser with regard to the operation of the heat interchanger.

Another object of this invention is to provide a. heat interchanger and condenser cooling control means which will maintain a constant temperature of refrigerant entering the compressor.

Other objects and advantages will appear from the following detailed description.

The accompanying drawing illustrates a form of'the invention and a description of the same will follow, it being understood that the invention is also capable of embodiment in numerous modified and amplified forms falling within the scope of the appended claims.

In the drawing,

Fig. 1 is a diagrammatic view of a refrigeration system with a cross sectional view of the denser water cooling control means, and

Fig. 2 is a diagrammatic view of a refrigeration system with a cross sectional view of the combination liquid receiver and heat interchanger 3 and an outlet connection 5. The details of the compressor are not shown, as any type of ap- .adapted to draw in gaseous refrigerant and ischargethe same in a compressed form is suitable. .The compressing apparatus may include an oil separator which will separate lubrieating oil, used to lubricate the compressor, from the refrigerant.

An electric motor I, with associated electrical connections 8, may be used to drive the compressor through a belt 9, although other methods of driw'ng the compressor or compressing the gas .may be used.

I A refrigerant such as sulfur dioxide or methyl chloride may be used in the system, the direction of flow thereof being indicated by the arrows in the drawing; After being compressed in the compressor, the refrigerant may flow through a pipe line H to a water cooled counterflow condenser H which is shown in diagrammatic form. The compressed gas may be cooled in the condenser, by means of water passing around the condenser coils through a pipe l3. The water enters the pipe through a valve l4 and is. discharged at the end of the pipe. The cooling action of the condenser changes some of the re-.

too much, it will have retained some of the heat.

received during the compression process. The invention is not limited to a water cooled condenser, it being possible to use any suitable con- The refrigerant flows from the liquid receiver through outlet 23 and line 3| to distribution valves 33 and 35 which divide the supply into two lines 31 and 39. Control valves 4| and 43 are located in the lines 31 and 39. These valves control the flow of refrigerant through the respective lines and may be of a type operable by electric means. Electrical connections to the control valves are represented by the numerals 42 and 44, which may be connected to thermostats or other means suitable for controlling the electrical circuit.

The refrigerant flows through the lines 31 and 39 to expansion valves 45 and 41 where the liquid refrigerant is allowed to expand in the evaporating coils 43 and 5| to a gaseous state, thus absorbing heat and cooling the respective enclosures 50 and 52. The gaseous refrigerant is then drawn by the compressor through lines 53 and 55, valves ,51 and 59, line 5|,T connection 63, heat interchanger coil 25, and line 65 to the compressor. The compressor capacity will be large enough to supply each of the evaporator coils with an amount of refrigerant which may be evaporated therein due to the heat absorbing action of the coil. If one of the evaporator coils be shut down or the supply of refrigerant thereto lessened by means 'of control valves 4| and 43, distributing valves 33 and 35, or adjustment of expansion valves 49 and 5|, the remaining evaporator coil will not be able to cause all the refrigerant supplied by the compressor to be evaporated since it would be receiving a much larger than normal amount of refrigerant. As a result some of the liquid refrigerant will be drawn into the line 6| from where it would be drawn into the compressor causing considerable damage were it not for the heat interchanger coil 25. The sudden shutdown of onecoil might also cause the remaining coil or coils to become too cold over a short period of time causing them to frost or freeze moisture thereon, thus decreasing the heat transfer capacity of the coils not shut down and allowing .even more unevaporated refrigerant to reach the compressor. When any liquid refrigerant reaches the heatinterchanger coil, it exchanges heat by means of conduction with the uncondensed gas or liquid contents of the liquid receiver, Since the refrigerant inthe receiver is relatively warm, because of heat received in the compression process, the liquid refrigerant in the suction line will be given enough heat to cause it to betotally evaporated into a gaseous state and thence pass on into the compressor.

In order to insure that the refrigerant leaving the condenser will retain enough heat to enable the heat interchanger to operate satisfactorily, an automatic condenser cooling control maybe provided and will now be described. The automatic condenser cooling control for a water cooledcondenser is shown in Fig. 1, where the water valve l4 may be controlled by a suction operated diaphragm 61 which may be incorporated with the water valve or connected externally therewith. Suction for the operation of this valve is supplied from the compressor suction intake through a T connection 69 and a line II. The suction in the line may be controlled by a thermostatic bulb or valve 13 which varies the suc tion in the line in accordance with the temperature of the refrigerant in the line 65. The thermostatic valve 13 and the suction operated diaphragm are connected so that any decrease in the temperature of the refrigerant entering the compressor through the line 65, will cause the thermostatic valve to operate the suction operated diaphragm through the suction supply line, to cause the amount of cooling water entering the condenser to decrease. A decrease in the amount of cooling water entering the condenser will cause the temperature of the refrigerant entering the liquid receiver to rise, which in turn will cause more heat to be interchanged with the refrigerant passing through the heat interchanger into line 65 and thus raise the temperature of the gas entering ,the suction side of the compressor.

Referring now to Fig. 2, I have there shown the heat interchanger in combination with an automatic air cooled condenser control. The numerals used in Fig. 1 designate the same parts in Fig. 2 and the operation of the systems are the same, the only modification being in the 30' condenser cooling system where the numeral 15 indicates a fan which may be connected to the compressor motor by any suitable means. The fan causes air to move over the condenser coils and to thus cool them. Adjustable shutters ll may be provided to control the flow of air over the condenser coils. The shutters may be connected by a rod 79 so that they move in unison. A suction operated diaphragm Bl is connected to the shutters by a rod 83. As in Fig. 1, suction is available to the diaphragm through the T connection 69, line M and thermostatic valve it. The thermostatic valve and diaphragm are' so connected that a decrease in the temperature of the refrigerant entering the compressor causes the diaphragm ill to close the shutters and thus raise the temperature of the refrigerant leaving the condenser and entering the receiver. This rise in temperature of the refrigerant entering the receiver raises the temperature of the refrigerant in the suction line of the compressor by means of the heat interchanger as before.

While suction operated valves have been described in-connection with the automatic condenser cooling control systems, it is possible to use electric solenoid operated or direct thermostatic bellows operated valves if desired, without changing the invention.

In some installations satisfactoryoperation of the heat interchanger may be attained without the automatic condenser cooling control and in such a system the water valve l4 may be oper-- ated manually or by other types of automatic control means.

- By the above methods the danger of liquid refrigerant reaching the compressor and the atv} tendant dangers are avoided. The heat exchange effected by the heat interchanger coil is also advantageous in reducing the temperature of the liquid refrigerant in the liquid receiver.

The numeral 90 indicates an auxiliary regulating valve which may be used in conjunction with the heat interchanger to compensate for a lack of balance between the load on the evaporating coils'and the capacity .of the compressor or a lack of capacity of the expansion valves on the evaporating coils to pass all the-refrigerant sup- I plied by the compressor. This valve is connected between the suction line entering the heat interchanger and the liquid receiver by means of connections 63 and I1, and may be of a type well known in the art, which will open automatically when a suction pressure drop takes place in the line entering the heat interchanger and closes automatically when the suction pressure rises again. This valve may also be operated by an electric solenoid or thermostatic means if desired. 4

It is to be understood that the refrigeration systemshown is only one of the many types of refrigeration systems to which the heat interchanger, automatic condenser cooling control, and auxiliary regulating valve may be applied. The system shown in the drawing was used as an example because of its simplicity. The many regulating devices such as thermostats, pressure control valves, manual valves and electrical switches usually employ-ed may be added to the system without changing the scope of the invention. Likewise, while for purposes of illustration only two evaporating units are shown, the heat interchanger and auxiliary regulating valve will function equally as well when any number of evaporat ng coils are used, it being only necessary to change the size of the various parts.

I claim as my invention:

1. A refrigeration system comprising a compressor, a condenser to receive the output of said compressor, a liquid receiver reservoir communicating with said condenser, an evaporating means communicating with said liquid receiver, a heat interchanger adapted to exchange heat with the contents of the liquid receiver, a return line con- 4 necting said evaporating means with said heat interchanger, said heat interchanger being connected with the inlet of the compressor, and a valve adapted to pass a portion of the output of the compressor into said heat interchanger.

2. A refrigeration system comprising a compressor, a condenser to receive the output of said compressor, a liquid receiver reservoir communicating with said condenser, an evaporating means communicating with said liquid receiver, a heat interchanger adapted to exchange heat with said liquid receiver, a return line connecting said evaporating means with said heat interchanger, said heat interchanger being connected with the inlet of the compressor, and a valve adapted to pass a portion of the output of the condenser into said return line, said valve being responsive to variations in the pressure in said heat interchanger.

3. In a refrigeration system, a condensing means, a liquid receiver reservoir communicating with the outlet of said condensing means, a coil within said receiver connected with the inlet of said condensing means, an evaporator communicating with said receiver, a return line from said evaporator to said coil, a cooling means for said condensing means and means to control the cooling means adapted to maintain the temperature of the contents of the receiver high enough to evaporate any liquid refrigerant returning to the condensing means through said coil.

4. A refrigeration system comprising a compressor, a condenser to receive the output of said compressor, a liquid receiver reservoir communicating with said condenser,an evaporating means 3 communicating with said liquid receiver, a heat interchanger adapted to exchange heat with said liquid receiver, a line connecting said evaporating means with said heat interchanger, a return line contents of the liquid receiver and a condenser cooling means adapted to be controlled by the temperature of a refrigerant entering the inlet of the compressor, and a valve adapted to pass a 4 portion of the output of the condenser into said heat interchanger.

6. In combination, a refrigeration compressor having an outlet and inlet therefor, a condenser connected with the outlet thereof, a liquid receiver communicating with said condenser, a heat interchanger connected with the inlet of the compressor and adapted to interchange heat with the contents of the liquid receiver and a valve adapted to by-pass liquid refrigerant into said heat interchanger. Y

7. In combination, a refrigeration compressor provided with an inlet and an outlet, a condenser connected with the compressor outlet, a liquid receiver reservoir communicating with said condenser, a heat interchanger connected with the compressor inlet and adapted to interchange heat with the contents of the liquid receiver, air circulating means to move air over the condenser, air flow control means adapted to regulate the amount of air passing over the condenser to maintain the temperature of the contents of the liquidreceiver high enough to evaporate any liquid refrigerant returning to the compressor through the heat interchanger.

8. In a refrigeration system, a condensing means, a receiver communicating with the outlet of said condensing means, a coil within said receiver connected with the inlet of said condensing means, an evaporator communicating with 'said receiver, a return line from said evaporator to said coil, and a valve adapted to pass a portion of the liquid refrigerant from the outlet of the condensing means into said .coil.

'9. In combination, a refrigeration compressor provided with an inlet and an outlet, a condenser connected with the compressor outlet, a liquid receiver reservoir communicating with said condenser, a heat interchanger connected with the compressor inlet and adapted to interchange heat with the contents of the liquid receiver, liquid cooling means to cool the condenser and control means I to regulate the liquid cooling means to maintain the temperature of the contents of the liquid receiver high enough to evaporate any liquid refrigerant returning to the compressor 

